Iceni 70cm Transverter from G4DDK - Part 1

I have plunged myself into the world of transverters by buying the 70cm Iceni from Sam Jewell G4DDK.

Here's a list of specifications from Sam's website.

Parameter	Measured	Comments
RX noise figure	2.0dB	Usual uncertainties apply
RX gain	21dB +/-1dB	Fixed Gain
RX maximum input	0dBm	Max non-damage level
RX IIP3	-10dBm +/-1dB	Measured at -37dBm/tone
RX bandwidth	8.5MHz	3dB bandwidth
TX gain	16.5dB +/-0.5dB	Tx attenuator at minimum
TX IF input level	0dBm	Max +6dBm at attenuator minimum
TX output power	+20dBm	At +6dBm IF input. 0dBm max IF input recommended
TX IMD	-50dBc/-38dBc	+7dBm/+10dBm per tone at output
TX spurious	<-60dbc	Except second harmonic -53dBc at +16.5dBm output

The kit doesn't on the face of it look too complicated, but care must be taken when assembling.   All the problems I encountered were all RTFM issues.

Sam suggested to mark and drill the tin enclosure first which went quite well until I had scribed the first few line on the box only to realise what I considered to be the top of the PCB was in fact the bottom, again an RTFM problem on my part.  Make sure you have sharp drill bits tin isn't the easiest material to drill though.  It took about 45 minutes to mark up and 10 minutes to drill.

Tin box marked and drilled.

To assemble the PCB you do need a good pair of tweezers, a decent eye glass and a fine tipped iron.  Sam  recommended using 0.8mm tin/lead mix solder but I went for solder paste instead, dabbing the correct amount on the pads using a cocktail stick, which was recommended to me by a friend.  The jury is still out on which way is best when the solder paste flowed correctly it was much easier and gave a good looking joint but you do need to keep the board clean and not apply to much paste.

I washed the board after fitting the resistors by soaking in a bath of isopropyl for an hour then agitating with a toothbrush to remove any small solder balls and left over paste.  Once the wash has been completed go over the joints with the eye glass checking that the paste hasn't just blobbed up onto the end the component and has in fact made a good joint.   I washed the board after fitting each set of components but omitted devices like the variable capacitors, electrolytic caps, variable inductors and the ADE-13 mixer all of which wouldn't take kindly to the ingress of solder paste.

If I was going to build another one I'd actually fit the ceramic caps first as most are coupling caps and so could easily be tested for shorts which wasn't the case once I had fitted the resistors.

The only device I had real trouble with was fitting the PSA4-5043 MMIC amps they're damn fiddlely to fit.  Now that I tried fitting them I'd have done it differently by fitting the main ground leg by using the 0.8mm solder to apply a blob on the ground pad and then using the tweezers slide the device into place while keeping the solder blob molten.    I found when using the paste as I couldn't see the solder pads getting the orientation wrong was all too easy.   I'm now awaiting for two replacements from Sam as I ended up damaging two of the devices trying to remove them due to the orientation issue.

You can see in the picture below how small the MMIC amps, circled in red, really are.  The markings on the green background are 1cm squares.

The Iceni with an MMIC encircled in red 

I had a couple of parts go awol in the construction which Sam has very kindly replaced gratis he did however charge me for the additional two MMIC's at three pounds each plus postage which is very fair.

Once the new parts arrive I'll need to fit the parts and then finally the MX1 and inductors I can then move onto the fitting the PCB into the tin box.

Part two coming soon.